The retina of the eye has two parts: the macula and peripheral retina. The macula is very small and in the center of the retina. The area surrounding the macula is the peripheral retina and makes up 95% of the retina.
The macula is necessary for normal central vision acuity and consists mostly of light-sensitive cells called cones. In macular degeneration, the light-sensitive cells are damaged and, thus, inoperative. Common causes of macular degeneration are age, diabetic retinopathy, ocular vascular accidents or disease, retinal dystrophies, central nervous system diseases, etc. The inoperative macula can create a very dim and blurred central spot in the vision field, called a scotoma, and the rest of the vision field can become dimmer than normal. The severity of the loss depends on the progression of the disease. In the advanced stages of macular degeneration, central vision may be reduced or completely lost making it impossible to read, watch television, drive, sew, etc.; however, the peripheral vision remains unaffected.
The peripheral retina provides side or peripheral vision for orientation in space and consists mostly of light sensitive cells called rods. The rods are more sensitive to light and motion than cones. The outer, peripheral part of the retina typically remains un-diseased and intact in persons with macular degeneration.
Surgical procedures, such as laser photocoagulation and photodynamic therapy, and therapeutic treatments, such as supplements or pharmaceutical agents have had mixed results for treatment of macular degeneration.
Additionally, vision aids such as eyeglasses fitted with special telescopes and magnifying glasses are commonly used by persons suffering from macular degeneration.
A bioptic telescope uses a plurality of lenses, constituting a Galilean telescope, to magnify the image formed on the retina of the eye and to provide light to the operative light-sensitive cells. However, the bioptic telescopes can only achieve a moderate image enlargement to a limited visual field and are cumbersome.
Magnifying glasses can provide image magnification and can be coupled with a light to assist in the transmission of light. However, distortion of the image increases with the power of magnification and the eyeglasses can be heavy due to the thickness of the lens.
Therefore, a need exists for a vision enhancing device for persons with macular degeneration that can redirect incident light away from the optic axis outwardly toward the un-diseased region of the retina.